The name protein comes from the Greek “proteios” meaning “first” since they have the highest importance between the molecules conforming the living beings. In vertebrates, proteins are the most abundant organic compounds, representing about 50% of the tissues, in a dry basis.
Practically, all biological processes depend on the presence and/or activity of these types of substances. Almost all enzymes, chemical reaction catalysts in living organisms, are proteins; many hormones, regulators of cellular activities; the hemoglobin and other molecules with transport functions in the blood; antibodies, in charge of natural defense actions against infections or foreign agents; cells receptors, to which molecules capable of developing a determined response are affixed to; actine and miosine, final responsible of the muscle shortening during a contraction; collagen, integrant of highly resistant fibers in holding tissues; these are only some examples to provide an idea of the variety and transcendence of their assigned functions.
Proteins are macro-molecules formed by amino acid chains, which are molecules having a free carboxyl group (—COOH) and a free amino group (—NH2). In all amino acid conforming proteins, except glycine, the alpha carbon is an asymmetrical carbon. There are about 20 different amino acids conforming proteins. The chemical bonding between amino acids in proteins is made by a peptide linkage. Hundreds and thousands of these amino acids can participate forming one protein molecule.
According to the protein shape, these may be classified in fibroses and globular, wherein the former have long amino acid chains, keratin and collagen are examples thereof. On the other hand, globular proteins are characterized by bending their chains in a tight or compacted spherical shape, such as most enzymes, antibodies, some hormones and transport proteins.
From the standpoint of human nutrition, protein consumption including the so called essential amino acids is vital, as the lack of these amino acids limits the organism development as being non-capable to replenish dead cells and tissues or to create new ones. Essential amino acids are: Valine (Val), Leucine (Leu), Isoleucine (Ile), Phenylalanine (Phe), Methionine (Met), Threonine (Thr), Lysine (Lys), Tryptophan (Trp), and Histidine (His).
Likewise, there are amino acids capable of being synthesized by the body, and they are referred as non-essential, these being: Arginine (Arg), Alanine (Ala), Proline (Pro), Glycine (Gly), Serine (Ser), Cysteine (Cys), Asparagine (Asn), Glutamine (Gln), Tyrosine (Tyr), Aspartic acid (Asp), and Glutamic Acid (Glu).
The human body synthesizes the non-essential amino acids, while those essential have to be provided by food. All animal and vegetal proteins have about the same 20 amino acids. The amino acids ratio varies as a function of the protein source. Nutritional quality of any protein is related to its amino acid composition, digestibility, and capability to supply essential amino acids in the required amounts to those organisms consuming the protein.
In order to evaluate the protein quality, traditionally the reference standard value referred as Protein Efficiency Ratio (PER) was used. The PER method reflects the amino acids requirements of young growing rats and not of human beings. However, in 1991, the experts of the Joint Consultative Meeting of the Food and Agriculture Organization of the United Nations, and the World Health Organization (FAO/WHO), published a report requesting the search of a more adequate and validated procedure for the protein quality evaluation, “Protein Digestibility Corrected Amino Acid Score” (PDCAAS), which has been accepted by the Food and Drugs Administration (FDA) in the United States for the evaluation of the protein quality and the labeling with nutritional information of products directed to children older than 2 years.
The PDCAAS is based in an amino acid scoring method, wherein the amino acid profile of the tested protein food is compared versus the amino acid requirement pattern established by the FAO/WHO for children between two and five years old. This pattern corresponding to children between two and five years old is used since they overcome the amino acid requirement pattern of older children and adults. The amino acid with a boundary value is used to establish the non-corrected amino acid score, and by multiplying said number by the food digestibility, the PDCAAS is obtained.
According to this method, the soy isolated proteins reach the maximum possible score (1.0) for the calculation of the corrected protein value. Any protein may have a PDCAAS value higher than 1.0. Soy proteins are complete proteins, highly digestible having all essential amino acids of the reference model in the right ratio. The pattern recommended by the FAO for proteins according to the PDCAAS is shown In Table 1.
TABLE 1FAO/WHO pattern for 2 to5 years old childrenMg/g proteinHistidine19Isoleucine28Leucine66Lysine58Methionine + Cysteine25Phenylalanine + Tyrosine63Threonine34Tryptophan11Valine35
In view of the above, there is always a need to develop feeding compositions and methods providing essential amino acids for human consumption. In the prior art, for example, in U.S. Pat. No. 4,054,677, a process to prepare vegetable protein concentrates, products produced therefrom and milk containing said concentrates as food substitute, are described. The method comprises the steps of: subjecting a weak acid and vegetal flour having protein contents to hydrolysis; subjecting an alkali with the vegetal flour having protein contents to hydrolysis; mixing both hydrolyzed solutions and neutralizing them up to a pH of between 6.7 and 7.1; concentrating the neutralized mixture until obtaining a low dry matter concentration, and then drying again. However, it is observed that a limiting feature in said process is that proteins are produced from flours, which are products derived from grains having to be processed, which increases the costs of the produced product in said patent.
A prior art process to obtain recombinant proteins is disclosed in U.S. Pat. No. 7,229,792, wherein the object is to achieve the proteins or polypeptides production during the growing of bacterial or other host cells, substantially culturing them on a solid or semi-solid nutrition media and including the DNA sequences of concern to codify the recombinant proteins under the control of an inducing-regulating promoter or a constitutive promoter. Bacteria are feed from a solid or semi-solid nutrition media and the recombinant protein to be produced is recovered by irrupting the bacteria's surface. As can be seen, this process requires living organisms, which are both sensitive to the media and highly specific, then requiring more controllable processes which allow the large-scale production of hybrid proteins.
Likewise, in the U.S. Patent Application No. 2004/0086613, hydro-thermal processes are shown, to prepare hybrid proteins having modified SS/SH bonds, thereby producing hybrid proteins having remarked functional properties. Such processes involve a treatment with steam of an aqueous protein solution having admixed at least two different proteins, in a heating device provoking a thermal shock and thus altering the protein conformation, followed by a relatively fast cooling to provoke the formation of the desired hybrids. By the process disclosed in said application, both animal and vegetal proteins may be processed, and the starting mixture might be modified in its pH value and/or supplemented with one or more additional ingredients such as salts, phosphates, fatty acids, polysaccharides, alcohols, aromatic compounds. However, there is the great inconvenience that said procedure is expensive from the standpoint of energetic consume, due to the use of steam, besides, the thermal shocks and the abrupt temperature changes may degrade the obtained protein.
Due to the drawbacks of the procedures found in the prior art for the production of proteins, as described above, a simple, practical and economic manner to overcome said drawbacks has been looked for, by developing a procedure which allows the large-scale obtaining of high nutritional value proteins, mainly by using accessible vegetal origin sources.